In driver assistance systems which take into account the vehicle surroundings, for example systems which support the motor vehicle driver in parking or systems which are used to maintain a sufficiently great distance from a preceding vehicle, it is necessary to effectively detect the surroundings. In systems for supporting the parking maneuver, for example, the surroundings are detected with the aid of ultrasonic sensors. If a larger area of the vehicle surroundings is to be monitored, in particular, radar sensors or cameras are also used.
Parking assistance systems which guide the driver into a parking space are discussed for example in DE-A 10 2004 047484 or also in EP-A 1 270 367. In parking assistance systems of this type, a parking space is first measured upon passing the space, and the driver is subsequently guided into the parking space with the aid of indications. The guidance into the parking space may take place in passive form, steering angle instructions as well as starting and stopping commands being transmitted to the driver, or it may take place in active form in which the driver receives only starting and stopping instructions, while the steering takes place automatically via a steering actuator system. The parking assistance system used specifies whether and how the vehicle may be guided from the present position into the parking space and also determines the end position for the parking maneuver.
During parking, the surroundings are monitored by distance-measuring sensors, which are generally situated in the bumpers of the vehicle. The distance to detected objects may be displayed to the driver, and the driver is warned of imminent collisions with surrounding objects. If the parking assistance system includes a rear assist camera, the driver also receives information about the area behind the vehicle with the aid of a video image. In the known systems, the driver has control over acceleration and deceleration during the parking maneuver. The parking speed is determined by the position of the accelerator pedal, and the driver is requested, shortly before reaching the end position of the parking maneuver, to brake the vehicle to a stop. In this system, the driver has full responsibility with regard to longitudinal guidance, i.e., of the forward and backward movements, at all times during the entire parking maneuver. In unforeseen situations, in particular, for example if a previously unidentified obstacle appears during parking, this results in the fact that the driver is independently responsible for a resulting unknown braking operation.
In the latest developments of parking assistance systems, the longitudinal guidance is also handled by automatic intervention into the drive and/or brake. In these systems, it is of fundamental importance that objects with which the vehicle may collide be detected in time, to prevent an imminent collision with the aid of a braking operation which is then to be initiated automatically.